1. Technical Field
The disclosure relates in general to a liquid crystal display (LCD) panel and an LCD device using the same, and, in some embodiments, to a multiple-domain vertical alignment (MVA) LCD panel and an LCD device using the same.
2. Description of the Related Art
In a multiple-domain vertical alignment (MVA) liquid crystal display (LCD) panel known to the inventor(s), the liquid crystal molecules in each specific domain tilt in different directions. FIG. 1A shows a known MVA LCD panel 10. The LCD panel at least includes a red pixel, a green pixel and a blue pixel. Each pixel 11 normally has four liquid crystal (LC) orientations, and such alignment is called 4-domain alignment as indicated by the arrows of FIG. 1A. The LC orientations are oblique to and respectively form an angle of 45 degrees with the X axis and Y axis of the LCD panel 10 for providing a wide angle function. Slits of the pixel electrode and protrusions of the counter electrode are arranged to form several boundaries for the liquid crystal orientations. A boundary is the disclination formed between liquid crystal molecules of different LC orientations and restricts the transmittivity of the backlight. Another MVA LCD panel known to the inventor(s) can improve the transmittivity by reducing the number of the liquid crystal orientations to two. Each color pixel still has two opposite liquid crystal orientations, and is still capable of providing a wide view angle. The liquid crystal orientations of the pixels are all parallel to or perpendicular to a long-axial direction of the color pixels.
FIG. 1B shows such another known MVA LCD panel 10′. The LCD panel 10′ at least includes a blue pixel 11′, a green pixel 12′ and a red pixel 13′. The liquid crystal molecules in the blue pixel 11′, the green pixel 12′ and the red pixel 13′ all have a first LC orientation X1 and a second LC orientation X2. The first LC orientation X1 is opposite to the second LC orientation X2, wherein the two LC orientations X1 and X2 are both parallel to a horizontal direction of the LCD panel 10′ and perpendicular to a long-axial direction L of the blue pixel 11′, the green pixel 12′ and the red pixel 13′. The LCD panel 10′ further includes several protrusions 14′ positioned in the color filter substrate and several slits 15′ positioned on the thin-film transistor substrate. The slits 15′ further connect to several fine slits 16′ such that the liquid crystal molecules tilt faster when driven by the electrical field. That is, the response speed of the liquid crystal layer is increased so as to speed up the changing in grey level. The protrusions 14′ are parallel to the long-axial direction L, the slits 15′ are parallel to the protrusions 14′, and the fine slits 16′ are perpendicular to the protrusions 14′. The blue pixel 11′, the green pixel 12′ and the red pixel 13′ respectively each have a protrusion 14′ and two slits 15′, wherein the one protrusion 14′ is respectively disposed at a central position of the blue pixel 11′, the green pixel 12′ and the red pixel 13′, and the two slits 15′ are respectively disposed at the two sides of the each protrusion 14′. The protrusions 14′ and the slits 15′ are used for controlling the liquid crystal orientations in the blue pixel 11′, the green pixel 12′ and the red pixel 13′. Compared with the 4-domain alignment LCD panel 10 (FIG. 1A), the transmittivity of the LCD panel 10′ whose pixels have the above 2-domain alignment design is increased by 16%. As there are only two liquid crystal orientations being parallel to the horizontal direction of liquid crystal panel 10′ (that is, there are only two domains), when the white color is displayed by way of the blue pixel 11′, the green pixel 12′ and the red pixel 13′, color shift will occur. For example, bluish green color shift will occur when viewed from the horizontal direction and yellowish color shift will occur when viewed from the vertical direction.
FIG. 1C shows a Commission International d'Eclairage (CIE) 1931 color space chromaticity diagram. The chromaticity diagram includes a red domain R1, a green domain R2 and a blue domain R3. The coordinate of the chromaticity of a white-displayed picture measured in the normal direction of the LCD panel 10′ (that is, viewed right from the normal top of the LCD panel 10′) is (0.28607, 0.2952) and is designated as the first coordinate point P1. The coordinate of the chromaticity of the same a white-displayed picture measured at an angle of depression of 60 degrees from a direction parallel to the first LC orientation X1 (FIG. 1B) of the LCD panel 10′ (that is, the chromaticity is measured when the view angle is 60 degree from the horizontal direction of the LCD panel 10′) is (0.28463,0.29907) and is designated as the second coordinate point P2. The coordinate of the chromaticity of the same white-displayed picture measured at an angle of depression of 60 degrees in a direction perpendicular to the first LC orientation X1 of the LCD panel 10′ (that is, the chromaticity is measured when the view angle is 60 degree from the vertical direction of the LCD panel 10′) is (0.38187,0.3782) and is designated as the third coordinate point P3. As indicated in FIG. 1C, the third coordinate point P3 is farther away from the blue domain R3 (that is, closer to the red domain R1 and the green domain R2) than the first coordinate point P1. Thus, the white color is more yellowish when the LCD panel 10′ is viewed from a view angle in a direction perpendicular to the first LC orientation X1 than when the LCD panel 10′ is viewed right from the normal top of the LCD panel 10′. On the other hand, when the LCD panel 10′ is viewed from a view angle of 60 degrees in a direction parallel to the first LC orientation X1, the white color is bluish green. And then when the LCD panel 10′ is viewed from the same view angle of 60 degrees, the LCD panel 10′ has a color difference of 0.1254 between a view at a view angle of 60 degrees from the direction parallel to the first LC orientation X1 and a view at a view angle of 60 degrees from the direction perpendicular to the first LC orientation X1 (the distance between the second coordinate point P2 and the third coordinate point P3). However, when the LCD panel 10 whose pixels have 4-domain alignment as indicated in FIG. 1A is measured, the coordinate of the second coordinate point P2 is (0.31007, 0.3293), and the coordinate of the third coordinate point P3 is (0.3142, 0.32957). That is, the white picture is yellowish when viewed from a horizontal or a vertical direction, and the color difference is only about 0.00414. Therefore, when observing from different directions, the user can hardly notice any difference in color shift, and then can hardly feel the color shift of the entire picture displayed by the LCD panel 10.
In summary, in the MVA LCD panel 10′, the displayed picture shows different tendencies of color shift when viewed from different directions. Despite that the transmittivity and brightness are improved through the design which uses fewer domains, different tendencies of color shift occur when the LCD panel 10′ is viewed from different directions, largely deteriorating the user's comfort in viewing the displayed pictures. In contrast, the MVA LCD panel 10 does not have noticeable color shift issues, but suffers from lower transmittivity and brightness. Thus, both transmittivity and color shift are issues to be considered.